Boat steering and reversing system

ABSTRACT

A system for controlling the forward and reverse operation of a boat having a propulsion unit mounted on the boat and rotatable to provide normal steering of the boat. Included is a mechanism for initiating a rapid rotating of the propulsion unit through a turn of approximately one-half circle to redirect the force of propulsion forwardly and thus provide reverse drive of the boat. The mechanism comprises a rotating gear associated with the propulsion unit itself for generating and applying a turning moment of force or torque for reorienting the propulsion unit through the half-circle turn. A detent means is coupled to the unit and selectively positioned by a manual control lever in the path of a stop mounted on the unit during its turning to retain it in either the forward or the reverse drive position.

[ Mar. 12, 1974 BOAT STEERING AND REVERSING SYSTEM Inventor: Joseph E.Smith, Birmingham,

Mich.

3,738,306 6/1973 Pinkerton ll5/35 Primary Examiner-Duanc A. RegcrAssistant ExaminerCharles E. Frankfort Attorney, Agent, or FirmHauke,Gifford, Potalidis &

I73] Assignee: Wolverine-Pentronix, lnc., Lincoln Dumont Park, Mich.1221 Filed: Aug. 28, 1972 ABSTRALT A system for controlling the forwardand reverse oper- [211 Appl' N05 284,179 ation of a boat having apropulsion unit mounted on Related Application Dam the boat androtatable to provide normal steering of [631 Continuatiomim an of Scr NO249 '68 Ma 1 the boat. Included is a mechanism for initiating a rapid1972 p y rotating of the propulsion unit through a turn of approximatelyone-half circle to redirect the force of 52 US. Cl. 114/144 R 115/35Propulsimforwardly and thus Pmide reverse drive of 51 Int. Cl B631125/42 the boat- The mechanism mPrises rotating gear [58] Field of Search115/34 35 17 18- associated with the P P "self for 114/144 154 155 ingand applying a turning moment of force or torque for reorienting thepropulsion unit through the half- [56] References Cited circle turn. Adetent means is coupled to the unit and selectively positioned by amanual control lever in the UNITED STATES PATENTS path of astop mountedon the unit during its turning g l t lto retain it in either the forwardor the reverse drive rcxere a.... 1,903,265 3 1933 Peck 115 35 l"3,486,478 12/1969 Halliday ll5/35 21 Claims, 7 Drawing Figures 3z- 2g 46I l -56 ZZ\ 40 I] 2 1 ll l l 1 27 l M 10- i /Z 1.3 .3 j ::j 1])PATENTEMAR 12 I974 SHEE! 3 OF 3 Fig -2 PATENTEDHAR 1 2 mm 3796 1'78 sum3 or 3 BOAT STEERING AND REVERSING SYSTEM REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of U.S.application Ser. No. 249,168 filed May 1, 1972 for Boat Steering andReversing Mechanism.

BACKGROUND OF THE INVENTION This invention relates to a steering andreversing system for boats or other watercraft in which there isprovided a propulsion unit adapted to provide .a variable magnitudethrust force generally rearwardly of the boat to move it in a forwarddirection. The invention is particularly suitable for use with apropulsion system in which the propulsion unit is rotated about asubstantially vertical axis to provide for controllable steering of theboat. The major directional control is through the selective directingof the thrust force through the propulsion unit itself, which mayincorporate a modified rudder construction when rudder effect isdesired.

The present invention may be applied to propulsion systems comprisingdual units and in which internal combustion engines are included fordriving the propellers and thus generating the thrust force.Alternately, the propulsion unit may be connected to a hydraulic motor,an electrical motor, a turbine engine, a Wankeltype engine, or any otherconvenient prime mover. The changeover between forward and reverseoperation of the boat is achieved by means of a rapid reversingmechanism which utilizes the reaction torque generated by a rotatingelement of the propulsion unit to reorient the thrust vector direction.

Prior art propulsion systems for watercraft disclose a variety of drivesystems in which there is generally included a propulsion unit,consisting of the propeller shaft housingand propeller, sometimes with amodified rudder or fin, which is manually rotatable for steering of theboat. An example of this type of mechanism is shown and described inU.S. Pat. No. 1,693,590. U.S. Pat. No. 1,866,482 discloses a similararrangement, but in which the motor unit is fixed to the boat hull andsteering is achieved by rotating the propulsion unit through a cable andbevel gear arrangement.

U.S. Pat. No. 1,824,213 is another example of a disclosure of anoutboard motor wherein the propeller housing is rotatably controlledrelative to the motor housing for steering of the boat. Rotating actionis provided in that case by the direct mechanical forces applied by asector gear and rack mechanism.

Other mechanisms are known, similar to that dis closed in U.S. Pat. No.1,774,956, in which the propulsion unit and steering unit include aturret-like structure which encloses the driveshaft and the lowermostprojecting portion of the propulsion unit. For normal steering, theturret-like structure is turned about a substantially vertical axisthrough a gear coupled to the steering wheel and in mesh with a ringgear mounted on the turret-like structure.

It is also known to rotate a propulsion unit through a turn ofessentially 180 in order to reverse the direction of the thrust forceand hence the direction in which the boat is driven. The mechanisms toprovide this rotating effect are for the most part directly operablethrough the steering wheel and the extent of turning is not preciselycontrollable by the operator. Additionally, relatively large magnitudeforces must be applied from an external source to provide the rapidchangeover between the forward and reverse direction.

All of the aforesaid arrangements are subject to the obviousdisadvantages arising from the face that the rotatable propulsion unititself is not visible to the operator and the steering wheel does notalways clearly indicate the exact angular position of the propulsionunit relative to the hull axis.

Other patents and publications have shown steering systems which makegeneral reference to the rapid turning of the propulsion unit through aturn approximating-. But while these in several cases, for example inU.S. Pat. No. 2,834,313, refer to providing a quick rotation, there isno actual disclosure of a working mechanism whereby such turning may beachieved.

The present invention provides a mechanism which I utilizes theresultant torque or reaction force generated as a result of applying adrive torque to the various rotating elements of the propulsion unit torapidly rotate the propulsion unit 180 from its original orientation toreverse the direction of travel of the boat.

SUMMARY OF THE PRESENT INVENTION The present invention thus relates to arapid reversal mechanism for reorienting a watercraft propulsion unit inwhich the reversing mechanism is operable by forces independent of thenormal steering system and without the need of a complicated reversedrive or gear train mechanism. The present invention in its simplestform includes a reverse control system in which a manually operateddetent-stop mechanism provides limits for rotation of the propulsionunit through a 180 turn between two arcuately spaced positions, onerepresenting the forward and the other' representing the reverseorientation of the thrust force. The mechanism itself in one embodimentis constructed to include an offset propeller to provide the torque torotate the propulsion unit in which the propeller is mounted.Alternately, the torque for rapidly rotating the propulsion unit may bederived from the reaction forces applied upon the propulsion unithousing and caused by drive torque applied to the propeller shaft. Inthis manner, the reversing control system needs only a manually operatedmeans to arrest the rotating of the propulsion unit in the positiondesired, while the turning force is rapidly generated through the unititself. The manually operated means includes a rockable lever which isoperated through a reversing control lever and cable arrangement.

BRIEF DESCRIPTION OF'THE DRAWINGS The present invention will bedescribed in the accompanying specification with reference to theaccompanying drawings in which like numerals are used to refer to likeparts which appear in the several views, and wherein:

FIG. 1 is a partly schematic, cross-sectional view of a propeller typepropulsion unit, with parts broken away;

FIG. 2 is a partly schematic, cross-sectional view of an alternateembodiment of the present invention, with parts broken away;

FIG. 3 is a sectional view taken along the line 3 3 of FIG. 2;

FIG. 4 is a partly schematic, cross-sectional view of a furtherembodiment of the present invention, with parts broken away;

shown in FIGS. 2 and 3.

DETAILED DESCRIPTION 7 With reference to FIG. I, the drawing illustratesthe basic parts of a boat propulsion unit I5 which is of the propellerdriven type. The propulsion unit is adapted for mounting on a boattransom, as will be shown in FIGS. 6 and 7 hereinafter, although thecontrol system of the invention may also be used in conjunction withpropulsion units of the inboard/outboard type as well as those mountedamidship or forward on the boat in a tunnel or in a well. Included inthe unit is a driveshaft 10 which is vertically disposed and providedwith a bevel gear 12 keyed to its lower end. A drive source, such as theoutput shaft of an internal combustion engine, not shown, is coupled tothe upper end of the driveshaft 10. The driveshaft 10 is enclosed withina steering tube 14. The steering tube 14 is connectible at anintermediate portion to the propulsion unit 15 through detents 40 or 42The steering tube 14 and the propulsion unit 15 are both rotatable bymeans of a steering control wheel and associated linkage to providenormal steering. Reference is made to the aforementioned U.S. Pat.application Ser. No. 249,146 for an explanation of an appropriatesteering system to be employed at the upper end of the steering tube 14.The lower portion of the propulsion unit 15 consists of a housing 16enclosing a propeller shaft 17 journalled for rotation between a pair ofspaced bearings 18. The right-hand end, as shown in the drawing, of thepropeller shaft 17 projects from the housing 16, and has a propeller 19mounted thereon. A bevel gear 20 is keyed to the propellershaft l7proximate its left-hand end and is in mesh with the bevel gear 12mounted at the lower end of the driveshaft 10 to be driven therefrom.The propulsion unit 15 is rotatable about a substantially vertical axisas a result of being mounted for free rotation relative to a supportingstrut 22, which in turn is fixedly mounted on the boat. The lowerportion of the supporting strut 22 is provided with a recessed annularbearing surface 24 accepting a radially extending flange 26 affixed to,or formed integral with, the top portion of the propulsion unit housing16. A segmented retainer ring 27, affixed to the end of the supportingstrut 22 by any convenient means such as bolts, not shown, maintains theflange 26 within the annular recess in the end of the strut 22, andthrust and other bearing members, not shown, may be disposed between theengaged surfaces to reduce friction. Unless otherwise restrained, thepropulsion unit housing 16 is thus free to rotate about a vertical axisrelative to the support strut 22 and also relative to the steering tube14.

As also shown in FIG. 1, a manual control is provided for effectingchangeover of drive between forward and reverse modes. The manualcontrol includes a reversing lever 28 which is pivotably mounted about ahorizontal axis on a pivot pin 30 affixed to the steering tube 14. Thelever 28 further includes an upstanding arm 32 to the end of which isattached a reverse cable 34. A pair of lateral arms 36 and 38 are eachpivotably mounted at an end detent of the lever 28 and are provided witha detent mechanism, 40 and 42, respectively. It will be seen that eachof the detent mechanisms 40, 42 is freely pivotably mounted on itsrespective arm 36, 38 so that according to the rocking movement of thelever 28 about the pin 30, one or the other of the detent mechanisms 40,42 is placed in the path ofa fixed stop 44, which stop is fixed to theupper surface of the flange portion 26 of the propulsion unit housingI6.

A manually operated lever 46 is schematically represented with the threepositions forward," neutral and reverse indicated by letter designationF, N and R, respectively. The propulsion unit 15 is illustrated at FIG.1 in its forward position in which the detent mechanism 40 is inabutment with the stop 44 to prevent rotating of the propulsion unithousing 16 relative to the steering tube 14 and thus direct the thrustforce from the propeller 19 in a generally rearward direction, whilepermitting controlled steering of the boat by rotating the steering tube14 about a vertical axis by means of the normal steering mechanism. Whenthe lever 46 is placed in its right-hand or reverse position, asdesignated by the letter R, the lever 28 will be rocked in a clockwisedirection to place the detent mechanism 42 in the path of the stop 44,thus finally arresting the rotation of the propulsion unit 15 at a pointsubstantially from its original or forward position. With the propeller19 turning, the drive gear 12 mounted on the lower end of the driveshaft10 will provide a torque force T to make a rotation of the propulsionunit 15 into its reverse operating position. The force T is directed, asindicated by arrow, to rotate the propulsion unit 15 in acounterclockwise direction about the axis of the driveshaft 10.

Also shown in the FIG. 1 drawing in block diagram form is a clutch 48which is operable in the intermediate or neutral position of the controllever 46 to provide for disengagement of the drive from the engineassociated with the driveshaft 10. The clutch 48 may either be amechanically operated dog-type clutch, a solenoid operated clutch, ahydraulic operated clutch, or the like. Examples of several clutchmechanisms suitable for use in connection with the present invention areshown and described in US. Pat. application Ser. No. 249,168hereinbefore referred to.

FIGS. 2 and 3 show an alternate embodiment of the present invention inwhich the basic parts of the propulsion unit 15, including thedriveshaft'lO, the bevel gear 12, the steering tube 14 and thepropulsion unit housing 16, are mounted on a boat rear transom, with therotation and changeover between forward and reverse operation providedby the turning of the propulsion unit 15 through a differently generatedtorque. The turning force applied to the propulsion unit 15 is providedby an arrangement whereby the propeller 19 is offset from the axis ofthe driveshaft l0. Included in the mechanism is a separate propellershaft 49 which is journalled at its right-hand end for rotation in abearing 50. The shaft 49 is also journalled for rotation at itsleft-hand end in a suitable bearing and support plate 52. The propellershaft 17, which carries the bevel gear 20, is likewise journalled forrotation in the plate 52. Drive is transmitted from shaft 17 to shaft 49through a gear set including a pinion gear 54 fixed to the righthand endof the shaft 17 and a pinion gear 56 fixed to the left-hand end of theshaft 49 and in mesh with the gear 54.

Reversing control is provided through a rockable lever 58, which ispivotably mounted as-shown, alternately and selectively positions thedetent mechanism 40 or 42 into or away from alignment with the stop 44extending from the upper surface of the propulsion unit 15. In a mannersimilar to the FIG. 1 embodiment, there is included a clutch 48 which isactuated in the neutral position by the control lever 46 to disconnectengine drive from the driveshaft 10. The detail of construction of theclutch 48 is omitted in the interest of brevity.

FIG. 4 shows a different embodiment of the present invention which issubstantially similar to the embodiment of FIG. 1 except that the clutch48 is located proximate the lower end of the driveshaft on which thegear 12 is fixed. The clutch 48 is positioned in an opening 58 formedcentrally in the propulsion unit 15. The entire propulsion unit 15 isrotated counterclockwise about the axis of the steering tube 14, whilethe operation of the reversing control lever 28 raises detent mechanism40 and lowers detent mechanism 42 into the path of the upwardlyextending stop 44. This stops and retains the propulsion unit 15 in itsforward or reverse operating position. In a similar manner to theembodiment of FIG. 1, the clutch 48 is operable in the neutral selectionposition of the lever 46 to disconnect drive from driveshaft 10 andhence from the propulsion unit 15. It will be understood that thesupporting struts 22 are attached to a suitable mounting bracket fixedto the boat transom.

While the present invention is generally illustrated and described withrespect to the propulsion unit 15 being mounted at the rear end of theboat, the invention is not so limited, but is equally adaptable forforward or amidship installation on a boat. The clutch 48 may be of theconventional type, either electrically or mechanically actuated, andused with a split-type driveshaft 10.

The FIG. 5 embodiment is substantially similar to the one disclosed inthe aforementioned US. Pat. application Ser. No. 249,l68 in FIG. 4thereof. The propulsion unit 15, which is connected at its upper end tothe steering tube 14, provides for rotating action and normal steeringof the boat. The control mechanism includes, in addition to the verticaldriveshaft 10, a neutral tube 60 which at its upper end is suitablyactuated through movement of the reversing cable 34. According to theoperation of the neutral tube 60, a separate clutch 62, which isslidably mounted relative to the propeller driveshaft 17 at itsleft-hand end, is used-to selec tively engage and disengage the lowergear from driving relationship with the propeller driveshaft 17. Theneutral control tube 60 has a sector gear 64 fixed to its lower end andin mesh with a pinion gear 66 fixed to the upper end ofa rod 68. The rod68 carries a lower cam disk 70 which is engageable with the forward endof a clutch pin 72. It will be understood that the gear 20 is afree-running gear rotatably mounted with respect to the propellerdriveshaft 17. When the neutral tube 60 and the sector gear 64 rotate,the neutral pinion gear 66 will then turn the cam 70 and cause it toprovide a depression of the clutch pin 72. The operation of the clutchpin 72 will move the clutch 62 and disengage it from the gear 20. Thebevel gear 20 thus is permitted to spin freely on the propellerdriveshaft 17, while the propeller 19 is not being rotated. A torque Tin the direction indicated by the arrow, is generated by the resistancewhich the gear 20 offers to the bevel drive gear 12. This torque willrotate the entire propulsion unit 15 once the reverse cable has beenoperated. The selection of forward or reverse operation is made by theactuation of the reversing control lever 46 which serves to rock thelever 28 either clockwise or counterclockwise to place the detentmechanism 40 or the detent mechanism 42 in limiting abutment with thestop 44.

FIG. 6 illustrates the manner in which a dual installation including twopropeller type propulsion units 15 are mounted on the transom 72 of aboat 74. Each of the two propulsion units 15 are mounted on a suitablebracket 76 with the units rotatable about their respective verticallyoriented driveshaft 10 in accordance with the operational explanationgiven in connectionwith FIG. I. The turning force for each unit 15 isderived from the rotation of its associated bevel gear 12. In order toneutralize side thrust forces, the propeller driveshaft l0 and theassociated right-hand propulsion unit 15 are rotated in acounterclockwise direction, while the driveshaft 10 and the associatedleft-hand propulsion unit 15 are oppositely rotated in a clockwisedirection. Thus, the turning moment applied to the right-hand unit iscounterclockwise, while the turning moment applied to the left-hand unitis clockwise, and the arcuate paths followed by the two units duringreversal changeover are in opposing directions as indicated by thearrows.

FIG. 7 shows a dual installation on a boat 74 of a pair of propulsionunits 15, each of which is constructed like the embodiment of FIG. 2,with the propulsion unit housing 16 and propeller in each case offsetrelative to the substantially vertical axis of the driveshaft 10. Inthis manner there is provided an opposite direction turning moment abouteach of the axes of rotation as indicated by the arrows. Here again theadvantage of the dual installation and of the particular embodiment ofthe unit used is that the side thrust forces are neutralized and thestability of the boat during direction changeover is greatly improved.

It will thus be seen that by the present invention in its severalembodiments there is provided a novel and improved boat propulsionsystem with a simplified mechanism for providing changeover betweenforward and reverse operation. The system requires no external force inits operation. A force of turning for the propulsion unit is generatedby the unique arrangement of elements associated with or within the unititself.

What is claimed is:

11. In a boat having a propulsion unit mounted on it and rotatable abouta substantially vertical axis, a drive means for providing a rotativedrive to said unit, a steering means, a means connected between saidsteering means and said propulsion unit for normally steering it in aforward direction, and a control system operatively connected to andcontrolling said propulsion unit for rapidly turning it about said axisthrough a turn of substantially to effect a changeover between forwardand reverse drive of the boat, said system including a stop mounted onsaid propulsion unit and a pair of oppositely disposed detents, eachselectively engageable with said stop to retain said unit in a forwardor in a rearward drive position, said unit operable to rotate itselfbetween said forward and reverse drive positions responsive to thetorque provided by said drive means.

2. The combination as set forth in claim 1 wherein said detents are bothsuspended from a common operating lever, said lever shiftable by areversing cable coupled thereto.

3. The combination as set forth in claim ll wherein said drive meanscomprises an engine driveshaft connected to said propulsion unit fordriving it, said propulsion unit further including a propeller and apropeller driveshaft mounted between said engine driveshaft and saidpropeller.

4. The combination as set forth in claim 3 wherein a pair of saidpropulsion units are mounted in spaced relationship on said boat, saidpropellers normally rotatable by said engine driveshafts in oppositedirections to null side thrust forces during changeover between forwardand reverse positions.

5. In a boat having a propulsion unit mounted on it and rotatable abouta substantially vertical axis, a steering means, a connecting meanscoupled between said steering means and said propulsion unit fornormally steering it in a forward direction, and a control systemoperatively connected to and controlling said propulsion unit forrapidly rotating it about said axis through a turn of substantially 180to effect a changeover be tween forward and reverse drive for the boat,said system including a substantially vertical driveshaft having a gearmounted thereon, a propeller, a propeller driveshaft having saidpropeller fixed proximate one end and a gear fixed proximate the otherend, said gears in mesh, a stop fixed to a substantially horizontalsurface of said unit, a pair of detents spaced approximately 180 apartand selectively engageable with said stop to retain said unit inposition after changeover between forward and reverse drive, said gearon said driveshaft operable to provide a torque force for rotating thepro pulsion unit during said changeover.

6. The combination as set forth in claim 5 wherein said detents aremounted at opposite ends of a lever, and a reversing cable is coupled tosaid lever for operating it.

7. The combination as set forth in claim 5 wherein an engine driveshaftis connected to said propulsion unit for driving it and wherein a clutchmeans is operably connected to said driveshaft for providing drivedisconnect from said propeller driveshaft.

8. The combination as set forth in claim 5 wherein a pair of saidpropulsion units are mounted and laterally spaced one from the other onsaid boat, each of said propulsion units having its propeller normallyrotated in a different direction to minimize side thrust during thechangeover between forward and reverse drive of the boat.

9. The combination as set forth in claim 6 wherein said lever ispivotally mounted at a point proximate with the axis of said verticaldriveshaft, said lever having an upstanding arm coupled to saidreversing cable.

10. In a boat having a propulsion unit mounted on it and rotatable aboutan upstanding axis, a steering means, a connecting means coupled betweensaid steering means and said propulsion unit for normally steering it ina forward direction, and a control system operatively connected to andcontrolling said propulsion unit for rapidly rotating it about said axisthrough a half-circle turn to effect a changeover between forward andreverse drive for the boat, said system including a substantiallyvertical engine driveshaft having a gear mounted thereon, a propeller, apropeller driveshaft having said propeller fixed to one end and a gearfixed proximate the other end and in driven relationship with said firstmentioned gear, said propeller drive shaft including a connecting meansfor offsetting said propeller and said propeller driveshaft relative tosaid axis, a stop fixed to said unit, a pair of detents arcuately spacedapart and singly engageable with said stop to retain said unit inposition after changeover between forward and reverse drive, saidpropeller operable to provide a torque force to said unit duringpropeller rotation.

H. The combination as set forth in claim 10 wherein said detents aremounted on a lever, said lever pivotally mounted and having one endcoupled to a reversing cable for positioning a selected one of saiddetents in the path of said stop.

12. The combination as set forth in claim 10 wherein said enginedriveshaft has a clutch means operatively connected thereto fordisconnecting its drive from said propeller shaft during saidchangeover.

13. The combination as set forth in claim 10 wherein said stop ismounted on an upper planar surface of said unit, said unit furtherincluding a lateral bearing extension supporting it for rotation aboutsaid axis.

14. The combination as set forth in claim 10 wherein said detents areeach mounted on a different downwardly extending lever arm, said armspivotally attached to a rockable lever for raising one of said detentsand lowering the other of said detents into operable relationship withsaid stop.

15. The combination as set forth in claim 10 wherein a pair of suchpropulsion units, each having a propeller, are mounted in spacedrelationship upon said boat, both of said propellers being angularlyoffset in opposite directions relative to their respective vertical axisto provide for their rotation between forward and reverse positions inopposite directions to null side thrust forces during said changeover.

16. In a boat having a propulsion unit mounted on it and rotatable abouta substantially vertical axis, a steering means, a steering cableconnected between said steering means and said propulsion unit fornormally steering it in a forward direction, a control systemoperatively connected to and controlling said propulsion unit forrapidly turning it about said axis through substantially a half-circleturn to effect a changeover between a forward and a reverse driveorientation relative to the boat, said system including a substantiallyvertical engine driveshaft connectable to an engine for receiving arotatable drive therefrom, said driveshaft aligned with said axis, afirst gear fixed to said driveshaft, a propeller and a propellerdriveshaft rotatably mounted in said unit, a second free-running gearassociated with said propeller driveshaft and in continuous driven meshwith said first gear, and a clutch means operably connected to saiddriveshaft for selectively disconnecting said second gear from saidpropeller driveshaft and interrupting drive to said propeller, aprojection extending from the surface of said propulsion unit and a pairof detents selectively engageable one at a time with said projection toarrest the movement of said unit in one of said orientations.

17. The combination as set forth in claim 16 wherein said detentscomprise a pair of detents rockably mounted and movable into and awayfrom opposed relationship to said projection on said propulsion unit.

18. The combination as set forth in claim 17 wherein a reversing cableis operably connected to said detents to operate one of same into' thepath of said projection on said propulsion unit.

19 In a boat having a propulsion unit mounted on it and rotatable abouta substantially vertical axis, a steering means, a connecting meansbetween said steering means and said propulsion unit for normallysteering it in a forward direction, and a control means operablyconnected to and controlling said propulsion unit for rapidly turning itabout said axis through a turn of substantially 180 to effect achangeover between forward and reverse drive of the boat, said controlsystem ineluding a stop means fixed on the upper surface of saidpropulsion unit, a pair-of spaced detents for arresting its rotation ina forward and a reverse drive position, respectively, and a rotatingmeans for providing a torque to said unit during changeover turning ofsaid propulsion unit.

20. The combination as set forth in claim 19 wherein said last mentionedmeans comprises a vertically oriented driveshaft aligned with said axisand a gear fixed to said shaft.

2l. The combination as set forth in claim I) wherein said last mentionedmeans comprises a propeller mounted on said unit and offset relative tosaid vertical axis.

1. In a boat having a propulsion unit mounted on it and rotatable abouta substantially vertical axis, a drive means for providing a rotativedrive to said unit, a steering means, a means connected between saidsteering means and said propulsion unit for normally steering it in aforward direction, and a control system operatively connected to andcontrolling said propulsion unit for rapidly turning it about said axisthrough a turn of substantially 180* to effect a changeover betweenforward and reverse drive of the boat, said system including a stopmounted on said propulsion unit and a pair of oppositely disposeddetents, each selectively engageable with said stop to retain said unitin a forward or in a rearward drive position, said unit operable torotate itself between said forward and reverse drive positionsresponsive to the torque provided by said drive means.
 2. Thecombination as set forth in claim 1 wherein said detents are bothsuspended from a common operating lever, said lever shiftable by areversing cable coupled thereto.
 3. The combination as set forth inclaim 1 wherein said drive means comprises an engine driveshaftconnected to said propulsion unit for driving it, said propulsion unitfurther including a propeller and a propeller driveshaft mounted betweensaid engine driveshaft and said propeller.
 4. The combination as setforth in claim 3 wherein a pair of said propulsion units are mounted inspaced relationship on said boat, said propellers normally rotatable bysaid engine driveshafts in opposite directions to null side thrustforces during changeover between forward and reverse positions.
 5. In aboat having a propulsion unit mounted on it and rotatable about asubstantially vertical axis, a steering means, a connecting meanscoupled between said steering means and said propulsion unit fornormally steering it in a forward direction, and a control systemoperatively connected to and controlling said propulsion unit forrapidly rotating it about said axis through a turn of substantially 180*to effect a changeover between forward and reverse drive for the boat,said system including a substantially vertical driveshaft having a gearmounted thereon, a propeller, a propeller driveshaft having saidpropeller fixed proximate one end and a gear fixed proximate the otherend, said gears in mesh, a stop fixed to a substantially horizontalsurface of said unit, a pair of detents spaced approximately 180* apartand selectively engageable with said stop to retain said unit inposition after changeover between forward and reverse drive, said gearon said driveshaft operablE to provide a torque force for rotating thepropulsion unit during said changeover.
 6. The combination as set forthin claim 5 wherein said detents are mounted at opposite ends of a lever,and a reversing cable is coupled to said lever for operating it.
 7. Thecombination as set forth in claim 5 wherein an engine driveshaft isconnected to said propulsion unit for driving it and wherein a clutchmeans is operably connected to said driveshaft for providing drivedisconnect from said propeller driveshaft.
 8. The combination as setforth in claim 5 wherein a pair of said propulsion units are mounted andlaterally spaced one from the other on said boat, each of saidpropulsion units having its propeller normally rotated in a differentdirection to minimize side thrust during the changeover between forwardand reverse drive of the boat.
 9. The combination as set forth in claim6 wherein said lever is pivotally mounted at a point proximate with theaxis of said vertical driveshaft, said lever having an upstanding armcoupled to said reversing cable.
 10. In a boat having a propulsion unitmounted on it and rotatable about an upstanding axis, a steering means,a connecting means coupled between said steering means and saidpropulsion unit for normally steering it in a forward direction, and acontrol system operatively connected to and controlling said propulsionunit for rapidly rotating it about said axis through a half-circle turnto effect a changeover between forward and reverse drive for the boat,said system including a substantially vertical engine driveshaft havinga gear mounted thereon, a propeller, a propeller driveshaft having saidpropeller fixed to one end and a gear fixed proximate the other end andin driven relationship with said first mentioned gear, said propellerdriveshaft including a connecting means for offsetting said propellerand said propeller driveshaft relative to said axis, a stop fixed tosaid unit, a pair of detents arcuately spaced 180* apart and singlyengageable with said stop to retain said unit in position afterchangeover between forward and reverse drive, said propeller operable toprovide a torque force to said unit during propeller rotation.
 11. Thecombination as set forth in claim 10 wherein said detents are mounted ona lever, said lever pivotally mounted and having one end coupled to areversing cable for positioning a selected one of said detents in thepath of said stop.
 12. The combination as set forth in claim 10 whereinsaid engine driveshaft has a clutch means operatively connected theretofor disconnecting its drive from said propeller shaft during saidchangeover.
 13. The combination as set forth in claim 10 wherein saidstop is mounted on an upper planar surface of said unit, said unitfurther including a lateral bearing extension supporting it for rotationabout said axis.
 14. The combination as set forth in claim 10 whereinsaid detents are each mounted on a different downwardly extending leverarm, said arms pivotally attached to a rockable lever for raising one ofsaid detents and lowering the other of said detents into operablerelationship with said stop.
 15. The combination as set forth in claim10 wherein a pair of such propulsion units, each having a propeller, aremounted in spaced relationship upon said boat, both of said propellersbeing angularly offset in opposite directions relative to theirrespective vertical axis to provide for their rotation between forwardand reverse positions in opposite directions to null side thrust forcesduring said changeover.
 16. In a boat having a propulsion unit mountedon it and rotatable about a substantially vertical axis, a steeringmeans, a steering cable connected between said steering means and saidpropulsion unit for normally steering it in a forward direction, acontrol system operatively connected to and controlling said propulsionunit for rapidly turning it about said axis through substantially ahalf-circle turn to efFect a changeover between a forward and a reversedrive orientation relative to the boat, said system including asubstantially vertical engine driveshaft connectable to an engine forreceiving a rotatable drive therefrom, said driveshaft aligned with saidaxis, a first gear fixed to said driveshaft, a propeller and a propellerdriveshaft rotatably mounted in said unit, a second free-running gearassociated with said propeller driveshaft and in continuous driven meshwith said first gear, and a clutch means operably connected to saiddriveshaft for selectively disconnecting said second gear from saidpropeller driveshaft and interrupting drive to said propeller, aprojection extending from the surface of said propulsion unit and a pairof detents selectively engageable one at a time with said projection toarrest the movement of said unit in one of said orientations.
 17. Thecombination as set forth in claim 16 wherein said detents comprise apair of detents rockably mounted and movable into and away from opposedrelationship to said projection on said propulsion unit.
 18. Thecombination as set forth in claim 17 wherein a reversing cable isoperably connected to said detents to operate one of same into the pathof said projection on said propulsion unit.
 19. In a boat having apropulsion unit mounted on it and rotatable about a substantiallyvertical axis, a steering means, a connecting means between saidsteering means and said propulsion unit for normally steering it in aforward direction, and a control means operably connected to andcontrolling said propulsion unit for rapidly turning it about said axisthrough a turn of substantially 180* to effect a changeover betweenforward and reverse drive of the boat, said control system including astop means fixed on the upper surface of said propulsion unit, a pair ofspaced detents for arresting its rotation in a forward and a reversedrive position, respectively, and a rotating means for providing atorque to said unit during changeover turning of said propulsion unit.20. The combination as set forth in claim 19 wherein said last mentionedmeans comprises a vertically oriented driveshaft aligned with said axisand a gear fixed to said shaft.
 21. The combination as set forth inclaim 19 wherein said last mentioned means comprises a propeller mountedon said unit and offset relative to said vertical axis.